Clinical Significance of Aspirin and NSAID Antiplatelet Interactions

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Concomitant use of aspirin and NSAIDs gives rise to a pharmcodynamic interaction that may interfere with aspirin’s antiplatelet effects.
Concomitant use of aspirin and NSAIDs gives rise to a pharmcodynamic interaction that may interfere with aspirin’s antiplatelet effects.

The use of low-dose aspirin for cardiovascular protection in elderly patients is routine clinical practice. Likewise, nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used to relieve various types of pain. There is widespread concomitant use of these 2 agents, giving rise to a pharmacodynamic interaction that can potentially impede the antiplatelet effects of aspirin. As a result, understanding the consequences of this interaction, particularly in elderly populations, is essential to ensure patient safety.

In a review article published in the Journal of Thrombosis and Thrombolysis, Paul Gurbel, MD, of the Johns Hopkins School of Medicine in Baltimore, and colleagues reviewed the current literature surrounding this interaction. They also assessed several contributing factors, including the timing of administration, specific agent used, and other dose-related effects.

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Erin D Michos, MD, MHS, of the division of cardiology at Johns Hopkins School of Medicine in Baltimore, Maryland, told Hematology Advisor, "Despite all the decades we have used both of these therapies and their widespread use, there is still a lot we don't know about their interactions."

"[Many] patients get started on medications that they don't actually need long-term, and then these drugs stay on their medication lists indefinitely," she added.

Over 20 Years of Clinical History

The first studies investigating the therapeutic value of NSAIDs were conducted in the 1990s, which examined their anti-inflammatory and analgesic properties through cyclooxygenase (COX) enzyme blockade. Two forms of this enzyme exist: COX-1, which is produced at a constant rate in human cells, and COX-2, which is induced in response to different proinflammatory stimuli, including shear stress, cytokines, and growth factors.

Aspirin inhibits the production of key platelet aggregation factors, such as thromboxane A2 and COX-1. When aspirin is coadministered with certain NSAIDs, the agents may interact at the level of platelet inhibition; however, the clinical relevance of this interaction is poorly understood. In addition, recent studies have suggested that prolonged NSAID use may cause other adverse cardiotoxic effects, such as the production of reactive oxygen species, which can lead to the development of cardiovascular disease.

Effects of Different NSAIDs

Various NSAIDs are available for clinical use in the United States, including agents from 6 different classes. Several studies have been conducted to better understand the interactions between specific NSAIDs and aspirin. These studies, reviewed by Dr Gurbel and colleagues, were varied in design, dosing, and timing of administration. However, taken together, they revealed that pharmacodynamic interactions were present, although they were highly variable depending on the NSAID used.

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